Characterization of psychrophilic enzymes in ice algal species with a sequencing protocol of DNA from an individual algal colony

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Ice algal species can grow just at the freezing point of seawater at below 0℃ and are often fond in a colored ice in the polar sea. These ice algal species must maintain their photosynthetic activities to grow at the low temperatures. We found these ice algal communities, which were constructed by many diatom species, at Saromako Lagoon, Hokkaido Japan. They also could grow and maintain their photosynthesis at the low temperatures. To estimate the maintenance mechanisms of their photosynthesis, we focused on the key enzyme of photosynthesis, ribulose 1, 5-bisphosphate carboxylase/oxygenase (EC. 4.1.1.39, RuBisCO here after) and determined the primary structures. As most of the ice algal species can not be incubated for a long time, it is hard to get an enough biomass for extraction of DNA. Isolation and amplification method of DNA from a single colony of algae (Iwatani, et al. 2002) were applied for this study and successfully determined the DNA sequences of large and small subunit of some ice algal RuBisCO.Although characteristic structures were not found in the small subunits, commonly different structures from those of the temperate diatom species were found in the large subunits of ice lagal RuBisCO, which constructed a loop between the a-helixes of #16 and #17. These structures of large subunits of ice algal RuBisCO could keep the flexibilities of these enzymes at low temperature